What Causes Irregular Periods,severe Heart Burn And Nausea?

Dear Doctor,

I was told that i am not ovulating, reason being that i do not get my period regularry, only every 3 months sometimes less sometimes more often, my las period was 11 February 2010 before that the 9th of November 2009. The last couple of weeks i suffer from severe hartburn and Nausea, my breast are tender especially my nipples, I also urinate frequently, I use no form of birth control. I also urinate frequently. Is there a possibility that i might be pregnant? Me and my fionce do have intercourse on a regular bases. Please help. Regards, Benita